Rethinking Cement (2017)

Rethinking Cement focuses on cement production, the single biggest industrial producer of emissions. Cement production causes 8% of global carbon emissions – more than the global car fleet.

The first stage of cement making is to transform limestone (calcium carbonate – CaCO3) into lime (CaO), thus releasing carbon dioxide (CO2) as a waste product. Over half of cement-related emissions are due to this chemical process. We can’t continue to use limestone in this way any more than we can keep burning coal.

Rethinking Cement shows how Australia can lead the world with zero carbon cement. We have the technology to wipe out emissions from cement in ten years, and with smart thinking, we can even turn cement into a carbon sink of the future.

A zero carbon cement industry

This report describes a pathway for tackling cement emissions involving the following five strategies:

Strategy 1: Supplying 50% of cement demand with geopolymer cement. The reactions involved in making geopolymer cements do not generate greenhouse gases, and therefore zero emission geopolymer cements are possible.

Strategy 2: Supplying 50% of cement demand with high-blend cements. Regular cement can be blended with other materials, reducing its carbon intensity. This strategy proposes increasing the proportion of replacement material to 70%, using fly ash, slag, clay and ground limestone.

Strategy 3: Mineral carbonation. This strategy employs a new technology, mineral carbonation, to capture the emissions from the remaining production of Portland cement. With mineral carbonation, waste carbon dioxide is captured and chemically sealed within rock.

Strategy 4: Using less cement. By designing structures to use concrete more efficiently, utilising high strength cement, and replacing concrete with timber, overall cement consumption could be reduced by around 15% in 10 years.

Strategy 5: Carbon negative cements. There is the long-term potential to develop magnesium-based cements which absorb carbon dioxide, and would therefore have a negative emissions profile.

Making It Happen

Governments and industry can support a rapid shift to a zero carbon cement industry. One powerful stimulus to all the technologies presented in this report would be a national policy putting a price on cement carbon emissions, including imported cement. The Australian Government could back up such a policy with a national target to reduce the carbon intensity of cement, which becomes progressively more stringent.

This target could be supported by public investment into research and deployment of low-carbon cements, similar to the support for renewable energy provided by the Clean Energy Finance Corporation and the Australian Renewable Energy Agency.

Governments should also introduce new regulations or incentives to encourage the use in cement production of stockpiled fly ash and other waste materials such as waste glass, red mud and bagasse ash.